Boron suboxide, with a stoichiometry designated as B6Ox (0.75<x>1) is a chemically inert, super hard material (defined as Hv>40 GPa), with a relatively low mass density (2.6 g/cc) that is used as an abrasive grit for polishing and grinding metals and in the formation of dense ceramic materials used in armor systems and cutting tools. A super hard material may be defined as a material having a Vickers hardness (Hv) greater than 40 GPa as measured by ASTM 384-11e1 Standard Test for Knoop and Vickers Hardness of Materials. One typical method of synthesizing boron suboxide is to mix elemental boron with an oxygen-containing boron compound, such as boron trioxide (B2O3) and heat treat the mixture in an inert gas atmosphere. The resulting reaction forms a boron suboxide powder in particulate form that must undergo further processing, such as a milling process, prior to ceramic processing.
A second typical boron suboxide synthesis method utilizes the reduction of a metal oxide, such as zinc oxide (ZnO), to deliver the oxygen necessary for boron suboxide synthesis. Elemental boron is mixed with the metal oxide and heat treated to approximately 1300 degrees Celsius to 1500 degrees Celsius in an inert gas atmosphere to yield a boron suboxide powder. However, the resulting boron suboxide powder must undergo further processing, such as acid leaching, to remove remnant metal impurity from the boron suboxide powder.
Therefore, the inventors have provided improved methods of preparing boron suboxide.